Was the bike designed with them? If so, how could they not be there?
Gussets were phased in to address frame cracking. So either your bike is before this fix was designed into the bike, or hopefully, after. Do a search, Jim has pics posted of a typical Miyata frame cracking. Cracks are noticable once you know where to look.
In a google search box, type in: miyata cracks site:bikeforums.net